The most interesting - glGetStringi work fine on gf9800gt (win10 x64) And 9800gt don't support GL_ARB_debug_output extension. But I can ask for the addresses of all the necessary functions of this extension, and it works!

GL_ARB_debug_output generally (but not always) requires you to use a debug context. It won't normally show up otherwise (and if it does, you're either paying for extra sanity checks, or it won't be very complete).

GL_ARB_debug_output generally (but not always) requires you to use a debug context. It won't normally show up otherwise (and if it does, you're either paying for extra sanity checks, or it won't be very complete).